I take back my Ride The Lightning nomination in favor of a different Metallica album to represent their first five albums. If I had to pick a Metallica album that best represents what they were at their peak, I'd pick the ...And Justice For All album:

I've been listening to this album a lot lately...and I've got to say this album is my all time favorite Metallica album. I have just always loved the progressive nature of the overall songs and music on this album. This album sold over 9 million copies alone in America and was on the US Billboard albums chart for a total of 123 weeks.
I love all of Metallica's first five albums almost equally and love their first seven albums (80's and 90's stuff) and my favorite album of theirs always changes between their first five albums, but ...And Justice For All (1988) best represents the amazing musical growth and evolution the band went through back in the day. But I keep my Black Album nomination just because of the amazing feat it just achieved. I deleted my Ride The Lightning post.
Plus, I have a nostalgic attachment to this album due to "One" being the first Metallica song I ever heard through playing Guitar Hero 3 and this album being the first Metallica/Metal CD I ever bought.
Anyways...sorry I know this isn't the Metallica Hall Of Fame and a Metallica forum, LOL. So I also nominate the Golden Age Of NASCAR Gaming (1998-2005):

Even if you aren't/weren't a NASCAR fan...what gamer especially sports gamers growing up in the Late-90's/Early-To-Mid-2000's didn't love playing EA Sports' NASCAR games and playing these games to win fictional races and cause fictional crashes? In many ways...playing NASCAR games back in the day could be way more exciting and entertaining than watching the sport itself.